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How to carry out quality control during the installation of process pipelines in chemical plants?

DataTime:[2024-5-12]

If the chemical plant is compared to a person, then: equipment must be the "heart part"; conveying raw materials, water, gas, finished products and other process piping is the "arteries and blood vessels", in the production process has a vital position. Therefore, at the beginning of construction, we must strictly control the quality of process piping installation, if the quality is not good, will greatly affect the normal production in the future; as a chemical construction unit, control the quality of process piping installation, is the key to the survival of the installation enterprise, but also the future production unit can be "safe production" guarantee.

How to carry out quality control during the installation of process pipelines in chemical plants?

Quality control of process piping construction, to start from the beginning of construction preparation to the end of the blowing, gas-tightness test to control the whole process, we can divide the project into the following three stages:

Preparation stage

To understand the characteristics of the project process construction, to determine the construction difficulties and quality problems are likely to occur in the main parts of the general should start from the following aspects:
1. Organizational structure:
The establishment of quality assurance system, organizational structure and quality management system, clear quality responsibilities of each management department, the implementation of the responsible person; and the project department personnel, once determined, the project is completed before the completion of the project is not a must, should not be replaced at will.
2. Technical aspects:
To be carefully familiar with the construction drawings, from the flow chart to understand the main role of each piece of equipment for the construction of the device, combined with the list of pipeline characteristics, familiar with the equipment connected between the various process pipelines of the medium, pressure, material, temperature, etc., for high temperature, high pressure, special materials, special media of the pipeline, which clarifies the main content of the quality control, the preparation of the project's process pipeline construction of the quality control of the main objectives;
In the review of the construction program, the quality standards, construction methods for major projects, quality assurance measures should be put forward clear and reasonable requirements.
3. Personnel training:
For the pipeline design material of this project, prepare welding process procedures, make qualified welding process assessment in line with the requirements of the specification, relevant training for welders, and obtain the welding qualification of the corresponding project.
4. Material Procurement:
According to the material, specification model and standard required by the material preparation plan, qualified material suppliers with processing and manufacturing capability and manufacturing qualification should be selected.
Material acceptance must meet the relevant requirements; quality certificate should be the original, the content should be consistent with the object and the data is true in line with the standard requirements; valves to the scene must also be carried out hydrostatic test, all alloy steel pipes, pipe fittings, valves, etc., must be carried out on the chemical composition of the retest (spectral analysis); high-pressure pipelines, fittings, valves, must be 100 percent of the retest.
5. Welding material acceptance:
Appearance of the packaging should not be damaged moisture phenomenon, packaging mark (model, brand, specifications, production date, production lot number) and the attached quality documents should be consistent, if inconsistent, must be rechecked.

Installation process

Before the construction of engineering and technical personnel must be technical briefing for construction personnel, the content of the briefing is mainly construction methods, quality assurance measures, quality standards and other content; to ensure the quality of prefabrication, you can avoid the weather, the environment on the construction of the impact of the construction of the more conducive to the construction of quality control. Installation process should pay attention to the following main aspects:
1. Under the material processing:
Mainly control the length of the pipe cutting, the straightness of the cut, the cleaning of the flying edge burr and bevel processing; DN100 mm pipe cutting below the general use of abrasive cutter into line, large caliber medium and low-pressure, the pipe is generally used in gas cutting or plasma cutting, beveling can be used in the handlebar sander grinding and processing.
High-pressure tube cutting and beveling processing, generally are used to complete the tube bed or beveling machine; cut straightness of the excess, will affect the uniformity of the gap between the group of tube mouth.
Bevel processing should also be carried out in accordance with the requirements of the regulations angle, bevel too large, will cause labor, materials and machinery waste, increase the cost of installation, bevel too small, easy to cause un-welded through, slag and other welding defects, therefore, the quality of the undercutting and processing process quality control, the ultimate goal is mainly to ensure the quality of welding and the installation of the size.
2. Marking:
Prefabricated pipe each weld must be well marked, especially alloy steel material and special material pipe.
Mark the welding date, welder number, weld number, in accordance with the single-line diagram of each pipe section with paint marked with a pipe line number and pipe section number, so as not to bring confusion to the installation, resulting in weld can not be traced, resulting in the delivery of information and the physical inconsistency of the pipeline with the use of special materials such as the position of the error; prefabricated pipe sections must be closed at the end of the mouth.
3. Welding:
Welding quality control is the most important control link in the construction of process piping, requiring welders to strictly follow the welding instructions; many factors affecting the welding quality, in addition to the impact of the pipe mouth grouping and beveling, but also by the quality of the welder, welding materials, weather conditions and other impacts.
Welding work in the workshop or on the ground, the environmental impact is small, the quality of relatively good control, the main control of the quality of welding material baking, in strict accordance with the implementation of the baking, distribution system, control the amount of welding rods each time the welder receives the amount of welding rods, supervise the normal use of welding rod barrel.
If the process requires pre-warming and heat treatment of the welded joints, must strictly control the pre-warming and heat treatment temperature of each channel, high-pressure pipe welding should also pay attention to the bottoming quality of non-destructive testing.
4. Installation:
Field installation of process piping is a difficult point of quality control, subject to field installation conditions and environmental factors, appropriate quality assurance measures should be taken when necessary.
The welded joints of field welding are generally fixed joints, the quality is more difficult to control, so be sure to control the following aspects:
In the prefabrication stage, each welder is observed and statistically qualified status, because people are the first element in the quality control chain; the quality of the on-site grouping of the pipe mouth must also be carried out in accordance with the requirements.
If you encounter wind, snow, rain, high humidity and other weather, you must require effective protective measures before allowing welding.
Alloy steel pipe flushing argon gas is very difficult, so it is the weakest link in the site quality control, but also should be the most important link in the quality inspection, you can take the flux skin or flux cored wire bottoming, but this process must be recognized through the welding process assessment, and the welder after the test qualified.

Construction Inspection

The quality of the project to a certain extent to rely on the test to measure, non-destructive testing, pressure testing, blowing as a necessary part of the installation of process piping, but also a means of the process of sweeping, but also the quality of the construction of the test. This requires that there must be certain planning arrangements, in strict accordance with the specification requirements for implementation.
Non-destructive testing than the class must be carried out in strict accordance with the specification requirements, each welder of each pipeline weld should be sampling to the discovery of unqualified weld, must be returned to qualified and doubled sampling, until qualified, otherwise the welder weld 100% testing; alloy steel pipe heat treatment should also be into the hardness measurement;
2. Test pressure
  • A. Before the test pressure: test pressure range of pipeline installation works in addition to painting, insulation has been completed in accordance with the design drawings, the installation quality in line with the relevant provisions; test pressure gauge has been calibrated, and in the weekly inspection period, its accuracy shall not be less than 1.5 level, the table's full scale value of the maximum pressure to be measured 1.5-2 times the pressure gauge shall not be less than 2; to be tested in the pipeline in the unrelated systems have been separated by blind, pipeline safety valves, rupture plates and instrumentation components, etc. The pipeline to be tested has been separated from unrelated systems by blind plates, and the safety valves, bursting plates and instrumentation components on the pipeline have been dismantled; before the pressure test, the air should be exhausted when injecting liquid.
  • B. All pipelines subject to non-destructive testing must be tested and approved by the relevant departments and units before the pressure test.
  • C. The ambient temperature should not be lower than 5℃ during the hydraulic test, and anti-freezing measures should be taken when the ambient temperature is lower than 5℃.
  • D. The pressure test process: hydraulic test should be slow pressure, to reach the test pressure, stabilize the pressure for 10min, and then reduce the pressure to the design pressure, stop the pressure for 30min, to the pressure does not fall, no leakage is qualified; for the pipeline of the big difference, the static pressure of the test medium should be recorded in the test pressure.
  • E. After the test pressure: blind should be removed in a timely manner, drain the liquid. Discharge of liquid should prevent the formation of negative pressure, and shall not be discharged anywhere.
3. Blowing
  • A. Blowing before the need to prepare a blowing program, the specific blowing method should be based on the requirements for the use of pipeline, the working medium and the degree of dirty pipe surface to determine. Steam pipeline should be steam blowing; non-thermal pipeline shall not use steam blowing.
  • B. For special requirements of the pipeline, must take the corresponding blowing method. Do not allow blowing equipment and piping should be isolated from the blowing system; blowing order should be according to the main, branch, drain pipe in turn, blowing out of the dirt shall not penetrate into the pipeline has been qualified.
  • C. flushing, it is appropriate to use the maximum flow rate, the flow rate shall not be less than 1.5m / s; water flushing should be carried out continuously to discharge the water color and transparency of the water and penetration of the mouth visually consistent with the qualified.
  • D. steam pipeline before blowing, should be warmed up, timely drainage, and should check the pipeline thermal displacement; blowing order should be warmed up - cooling - and then warmed up the order of the cycle. At the same time, the flow rate should not be less than 3m/s.
  • E. After the pipeline blowing and resetting, no other operations shall be carried out to affect the cleanliness of the pipeline.

Summarize

The quality of a project determines the service life of the project, a good evaluation of the owner may give the construction unit in the market to establish a good image, a good image can bring a good space for development.
In the environment of increasingly fierce market competition, quality will be a very critical link as one of the many weights. Only strict quality control can have greater development.

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